1. Field of the Invention
The present invention relates to a color cathode-ray tube and, more particularly, to a color cathode-ray tube having a faceplate the internal surface of which is provided with a light scattering film for scattering external light.
2. Description of the Prior Art
In general, color cathode-ray tubes have a faceplate the internal surface of which is provided with antiglare means (for preventing glare) in order to prevent a display image from being visually impaired when external light which has entered the faceplate is reflected by a phosphor screen and the reflected light again passes through and exits from the faceplate.
As conventional internal-reflection preventing means, it is well known to erode the internal surface of a glass-made faceplate with ammonium fluoride or the like and form a multiplicity of irregularities on the internal surface by such erosion. In this case, a black matrix of predetermined shape is formed on the internal surface of the faceplate of the color cathode-ray tube on which such irregularities are formed, and three color phosphor layers are sequentially formed on the black matrix, thereby forming a required color fluorescent screen. In the color cathode-ray tube having the above-described constitution, external light which has entered the faceplate is scattered by the multiplicity of irregularities formed on the internal surface of the faceplate, whereby reflected light is prevented from exiting from the faceplate to prevent degradation of contrast.
The aforesaid known internal-reflection preventing means is capable of scattering external light, which enters the faceplate of the color cathode-ray tube, by means of the multiplicity of irregularities formed on the faceplate and preventing reflected light from exiting from the faceplate, but has various problems which will be described below.
A first problem is that the multiplicity of irregularities formed on the internal surface if the faceplate are deformed during panel cleaning which is performed before the black matrix is formed on the internal surface of the faceplate of the color cathode-ray tube. As the number of panel cleanings increases, the multiplicity of irregularities decrease in size, so that the internal-reflection preventing effect on the internal surface of the faceplate is reduced.
A second problem is that the treatment cost required to form the multiplicity of irregularities on the internal surface of the faceplate of the color cathode-ray tube is high and the formed multiplicity of irregularities is difficult to maintain.
A third problem is that if serious defects such as scratches occur in the internal surface of the faceplate of the color cathode-ray tube, it is impossible to regenerate the color cathode-ray tube.
A fourth problem is that if the black matrix is formed by using a fluorescent screen forming method based on a known photolithography, the shapes of black matrix holes are degraded.
Another internal-reflection preventing means using interference of light is known. For example, Japanese Patent Laid-Open No. 58739/1988 states that a layer of low index of refraction and a layer of high index of refraction are formed on the internal surface of a panel so that an anti-reflection effect can be obtained from interference of light. However, it is difficult to form the internal-reflection preventing means using interference of light.
Still another internal-reflection preventing means having progressively decreasing indexes of refraction is known, and this is one modification of the aforesaid internal-reflection preventing means using interference of light. For example, Japanese Patent Laid-Open No. 250540/1991 describes an anti-reflection film which is formed by coating the internal surface of a faceplate with an alcohol solution of Si(OR)4 (R: alkyl group) which contains SiO2 particles and firing the alcohol solution. This internal-reflection preventing means is also difficult to form, and is poor in mass-productivity since it is necessary to arrange the particles in a layer and fill the clearances between the particles with a hydrolyzed substance of Si(OR)4.
The present invention is intended to solve the above-described problems, and its object is to provide a color cathode-ray tube including antiglare or nonglare means which can be regenerated without degradation of its antiglare function and which can be inexpensively formed.
To achieve the above object, in accordance with the present invention provides, as first means, a light reflecting film composed of metallic-compound micro-particles having a high index of refraction and a particle size of 0.1 xcexcm to 2 xcexcm is provided on the internal surface of the faceplate of the color cathode-ray tube. The term xe2x80x9clight scattering filmxe2x80x9d means a film which yields an antiglare effect by scattering light.
To achieve the above object, in accordance with the present invention, as second means, a light scattering film is provided on the internal surface of the faceplate of a color cathode-ray tube, the light scattering film being composed of at least one of a black matrix film which contains graphite and metallic-compound micro-particles having a high index of refraction and a particle size of 0.1 xcexcm to 2 xcexcm and a precoat film which contains metallic-compound micro-particles having a high index of refraction and a particle size of 0.1 xcexcm to 2 xcexcm.
According to the first means, external light incident on the faceplate is scattered by the light scattering film which is formed on the internal surface of the faceplate, so that reflected light can be prevented from passing through and exiting from the faceplate, thereby preventing degradation of contrast. The light scattering film can be regenerated, and it is possible to form the light scattering film inexpensively compared to the formation of irregularities by erosion.
According to the second means, external light incident on the faceplate is scattered by each of the black matrix portion and the light scattering film portion which are formed on the internal surface of the faceplate, so that reflected light can be prevented from passing through and exiting from the faceplate, thereby preventing degradation of contrast. The precoat film and the black matrix film can be regenerated, and it is possible to form these films inexpensively compared to the formation of irregularities by erosion.